Photocatalysis has shown great potential as a green technology to help solve the energy shortage and environmental pollution issues. Since the conventional photocatalytic material TiO2 can only absorb UV light, it is highly desirable to develop new photocatalytic materials that harvest photons over a wide range of visible wavelengths or even into the infrared region, from the perspective of practical applications. This chapter introduces general principles and an outline of the current status in developing new photocatalytic materials.